Spasticity, contracture, and muscle weakness are major sources of disability following brain damage, and their development and recovery are closely interrelated. Increased resistance to passive movement in spastic hypertonia can be due to reflex (with both tonic and phasic components) and/or non-reflex (with both viscous damping and elastic stiffness components) changes. The various components contributing to spastic hypertonia and functional deficits following stroke, and the outcome of an intelligent stretching treatment in changing these components and functional performance will be investigated over 7 months for each patient. The first specific aim is to treat/stretch spastic ankle joints in stroke patients safely and repeatedly to joint extreme positions until a pre-specified peak resistance torque is reached with the stretching velocity adjusted constantly and inversely proportional to the resistance torque. The second specific aim is to evaluate pathophysiological changes in spastic hypertonia and to assess outcome of the stretching treatment in terms of both reflex (dynamic and static stretch-reflex gains corresponding to phasic and tonic reflex actions, respectively) and non-reflex (joint elastic stiffness and viscous damping characterizing displacement- and velocity- dependent resistances, respectively) changes in spastic ankles of stroke patients through in vivo experiments under both passive (muscle relaxed) and active muscle contracting) conditions over a period of 4 months. The third specific aim is to investigate stretching-induced changes in functional performance and the underlying mechanisms in terms of muscle force-generating capacity, maximum voluntary contraction (MVC), mechanical properties of the Achilles tendon and aponeurosis investigated using ultrasonography, torque-angle relationship of the triceps surae muscles, plantar and dorsi flexor co-contraction, and active ROM before and after stretching and over the period of 4 months. The long-term goals are to provide effective, convenient, and low-cost treatments of spastic limbs in neurologically impaired patients with quantitative outcome evaluation in multiple aspects.